those lutherans and calvinistsmight be on to something
I heard today, from a Lutheran pastor leading a Waldesian (Italian protestant) church about the interesting situation with the Lutherans and Calvins. First off, Luther and Calvin differed on two main points of theology: communion and politics. Luther believed that the substance of Jesus came into the bread and wine as they were being eaten, whereas Calvin said that Jesus was only present in the Holy Spirit. In terms of politics, Calvin taught that the Bible was the only guide for all of life, spiritual and secular, which contrasts with Luther's claim that God acted in the world in two parallel ways: the church and the state, separately.
Now, the exact nature of the differences aren't what important here. Over the years, these two differences have become less and less pronounced. Both the Lutherans and Calvinists recognized this. In North American, some people might have tried to combine all the Lutheran and Calvinist denominations into one überdenomination, but these Germans took a different approach.
Sometime in the 1970's, a bunch of denominations signed a treaty of sorts that allowed pastors trained and ordained in one of the denominations to serve churches in any of the other denominations. I don't know any of the details, but it seems like a remarkably smart idea, that allows for open fellowship between denominations, while recognizing the inevitable differences of opinion.
(by the way, everything here is completely unresearched. I'm just repeating what I remember of what the pastor said.)